package xianchengpool;

import java.io.IOException;
import java.util.Arrays;
import java.util.Random;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.RecursiveAction;
import java.util.concurrent.RecursiveTask;

/**
 * @功能
 * @创建时间 2019/12/26
 */
public class T12_ForkJoinPool {
    static int[] nums = new int[1000000];
    static final int MAX_NUM = 50000;
    static Random r = new Random();

    static {
        for(int i=0; i<nums.length; i++){
            nums[i] = r.nextInt(100);
        }
        System.out.println(Arrays.stream(nums).sum()); // stream api
    }
/*    static class AddTask extends RecursiveAction{
        int start,end;
        AddTask(int s,int e){
            start = s;
            end = e;
        }
        @Override
        protected void compute() {
        if(end-start <= MAX_NUM){
            long sum = 0l;
            for(int i =start;i<end;i++)
                sum += nums[i];
            System.out.println("from"+start+"to:"+end+"="+sum);
        }else {
            int middle = start +(end - start)/2;

            AddTask subTask1 = new AddTask(start,middle);
            AddTask subTask2 = new AddTask(middle,end);
            subTask1.fork();
            subTask2.fork();

        }
        }
    }*/
  static class AddTask extends RecursiveTask<Long> {
    int start, end;

    AddTask(int s, int e) {
        start = s;
        end = e;
    }

    @Override
    protected Long compute() {
        if (end - start <= MAX_NUM) {
            long sum = 0l;
            for (int i = start; i < end; i++)
                sum += nums[i];
            return sum;
        }
        int middle = start + (end - start) / 2;
        AddTask subTask1 = new AddTask(start, middle);
        AddTask subTask2 = new AddTask(middle, end);
        subTask1.fork();
        subTask2.fork();
        return subTask1.join()+subTask2.join();
    }
}
    public static void main(String[] args) throws IOException {
        ForkJoinPool f = new ForkJoinPool();
        AddTask task = new AddTask(0,nums.length);
        f.execute(task);
       // long result = task.join();
        // System.out.println(result);
        System.in.read();
    }
}
